Device and method for operating a bending beam in a closed control loop

Abstract

The present invention relates to a device for operating at least one bending beam in at least one closed control loop, wherein the device has: (a) at least one first interface designed to receive at least one controlled variable of the at least one control loop; (b) at least one programmable logic circuit designed to process a control error of the at least one control loop using a bit depth greater than the bit depth of the controlled variable; and (c) at least one second interface designed to provide a manipulated variable of the at least one control loop.

What is claimed is: 
     
       1. A device for operating at least one bending beam in at least one closed control loop, the device comprising:
 a. at least one first interface designed to receive at least one controlled variable of the at least one control loop; 
 b. at least one programmable logic circuit designed to process a control error of the at least one control loop using a bit depth that is greater than the bit depth of the controlled variable, the programmable logic circuit further being designed to operate the at least one bending beam in at least two of the following operating modes: a contact mode, a non-contact mode, an intermittent mode and a step-in mode, and the programmable logic circuit moreover being designed to switch over between at least two of the operating modes of the bending beam without losing control over a position of the bending beam; and 
 c. at least one second interface designed to provide a manipulated variable of the at least one control loop;
 wherein the bit depth of the control loop corresponds to the number of bits used to represent integers in a range in a binary representation of the control loop, and the bit depth of the controlled variable corresponds to the number of bits used to represent integers in a range in a binary representation of the controlled variable. 
 
 
     
     
       2. The device of  claim 1 , wherein the manipulated variable of the at least one control loop has a bit depth that corresponds to the bit depth of the controlled variable of the at least one control loop. 
     
     
       3. The device of  claim 1 , wherein the manipulated variable of the at least one control loop has a bit depth that is greater than the bit depth of the controlled variable of the at least one control loop. 
     
     
       4. The device of  claim 1 , wherein the at least one programmable logic circuit has a data reduction unit designed to bring the bit depth of the manipulated variable of the at least one control loop into line with the bit depth of the controlled variable of the at least one control loop. 
     
     
       5. The device of  claim 4 , wherein the data reduction unit is designed to reduce the bit depth of the at least one manipulated variable of the at least one control loop by omitting one least significant bit or by omitting multiple least significant bits. 
     
     
       6. The device of  claim 1 , further having: at least one third interface designed to input at least one parameter for adjusting the at least one control loop. 
     
     
       7. The device of  claim 6 , wherein the at least one parameter has a bit depth that is less than or equal to the bit depth of the controlled variable of the at least one control loop. 
     
     
       8. The device of  claim 6 , wherein the at least one parameter comprises at least one element from the group comprising: a gain of the controller, a reset time of the controller and a derivative-action time of the controller. 
     
     
       9. The device of  claim 6 , wherein the at least one programmable logic circuit is designed to manipulate the at least one parameter with the control error without previously performing a data reduction. 
     
     
       10. The device of  claim 1 , wherein the first interface comprises an analogue-to-digital converter and the second interface comprises a digital-to-analogue converter, and wherein a sampling rate of the analogue-to-digital converter is greater than a conversion rate of the digital-to-analogue converter. 
     
     
       11. The device of  claim 1 , wherein the programmable logic circuit is designed to set the manipulated variable of the at least one control loop to a predefined value before switching over the operating mode of the bending beam. 
     
     
       12. The device of  claim 1 , wherein the programmable logic circuit is designed to start a proportional component of the control of the at least one control loop from a value of zero after switching over an operating mode. 
     
     
       13. The device of  claim 1 , wherein the programmable logic circuit is designed to move the bending beam towards a sample surface and/or away from the sample surface over a predefined distance at a predefined speed. 
     
     
       14. The device of  claim 1 , wherein the programmable logic circuit comprises at least one element from the group comprising: a programmable logic array (PLA), a complex programmable logic device (CPLD) and a field programmable gate array (FPGA). 
     
     
       15. The device of  claim 1 , wherein the at least one bending beam comprises an element from the group comprising: a cantilever having a measuring tip of a scanning probe microscope, a probe arrangement for a scanning probe microscope having at least two probes that have different measuring tips for examining and/or preparing a sample, and at least one micromanipulator for preparing a sample. 
     
     
       16. A scanning probe microscope comprising at least one device of  claim 1 . 
     
     
       17. A method for operating at least one bending beam in at least one closed control loop, the method having the steps of:
 a. receiving at least one controlled variable of the at least one control loop; 
 b. using at least one programmable logic circuit to process a control error of the at least one control loop using a bit depth that is greater than the bit depth of the controlled variable; 
 c. providing a manipulated variable of the at least one control loop; 
 d. the programmable logic circuit operating the at least one bending beam in at least two of the following operating modes: a contact mode, a non-contact mode, an intermittent mode and a step-in mode; and 
 e. the programmable logic circuit switching over between at least two of the operating modes of the bending beam without losing control over a position of the bending beam;
 wherein the bit depth of the control loop corresponds to the number of bits used to represent integers in a range in a binary representation of the control loop, and the bit depth of the controlled variable corresponds to the number of bits used to represent integers in a range in a binary representation of the controlled variable. 
 
 
     
     
       18. A computer program comprising instructions that prompt a computer system to perform the steps of the method of  claim 17  when the computer program is executed by the computer system. 
     
     
       19. The scanning probe microscope of  claim 16 , wherein the at least one programmable logic circuit has a data reduction unit designed to bring the bit depth of the manipulated variable of the at least one control loop into line with the bit depth of the controlled variable of the at least one control loop. 
     
     
       20. The scanning probe microscope of  claim 16 , wherein the at least one device further comprises: at least one third interface designed to input at least one parameter for adjusting the at least one control loop. 
     
     
       21. The method of  claim 17 , wherein the manipulated variable of the at least one control loop has a bit depth that corresponds to the bit depth of the controlled variable of the at least one control loop.